Project Abstract Over the past several years, bacterial contamination of platelets has been the greatest transfusion-transmitted infectious risk in the United States. Bacterial contamination of platelet components occurs because of its unavoidable storage temperature (22 C), resulting in recognized transfusion-transmitted sepsis in at least 1 of 100,000 recipients, and an immediate fatal outcome in 1 in 500,000 recipients. Currently, the gold-standard tests for bacterial contamination of platelets rely on limulus amebocyte lysate (LAL), the aqueous extract of the blood of horseshoe crabs, which forms a clot or gel upon exposure to bacterial endotoxin. Due to the unsustainability of the LAL method, several new alternative technologies using chromogenic, chemifluorescent, or chemiluminescent assays have been introduced into the market; however, they continue to have serious limitations in terms of performance and spectroscopic range (both in time and wavelength). Photon Biosciences, LLC and S2Media (S2M Enterprises, LLC) have engineered a new, non-photobleaching luminescent protein named RECAL, which we intend to use as the basis for a fully quantitative, highly sensitive, rapid assay kit for checking for bacterial contamination of platelets.